What happened

Police agencies across the US positioned AI-powered ALPR-equipped patrol cars and fixed roadside units near demonstrations, activist meet-ups, and political gatherings, capturing and storing plate numbers, timestamps, and location data of vehicles attending or passing by protests.

In Phoenix, Arizona, police used surveillance, including license plate readers and drones, to track leaders of a Black Lives Matter protest for hours, seeking a pretext for arrest.

In Texas, police used an ALPR network to search for a vehicle corresponding to a rally highlighting the mental health impact of immigration policies, logging the reason as "protest veh."

The data, often including images of the vehicle and sometimes its occupants, is aggregated into massive, searchable databases, sometimes shared with thousands of other agencies, including federal entities like US Customs and Border Protection (CBP) and Immigration and Customs Enforcement (ICE). 

The incident occurred over several months, often around major protests, and created a detailed map of individuals’ political activities, associations, and movements. 

The potential harms included chilling effects on free speech and assembly, exposure of vulnerable groups (such as immigrant-rights activists or environmental organisers), risks of data misuse, and long-term retention of sensitive political-activity information in government databases and private vendor systems. 

Why it happened

The incident stemmed from expanding police adoption of ALPR technologies without sufficient oversight, alongside weak transparency around how data was collected, shared, and retained.

Many agencies relied on vendor systems that automatically shared data with regional and national networks, and policies governing protest-related scanning were unclear or nonexistent. 

Limited public accountability, opaque procurement processes, and inadequate guardrails against surveillance of constitutionally protected activities contributed directly to the problem.